Graceful shutdown

Graceful shutdown - pattern which helps to stop the application without losing data or killing running processes (for example, response to /start).

What are your last words?

Signals

• SIGINT (Signal Interrupt)

This signal sended when user presses Ctrl+C.

• SIGTERM (Signal Terminate)

This signal is often sent by process managers (like Docker, Kubernetes, or systemd) when they need to terminate a process.

so we want to handle both.

Example

Imagine you have a bot on webhooks with analytics usage.

import { app } from "./webhook";
import { bot } from "./bot";
import { posthog } from "./analytics";

const signals = ["SIGINT", "SIGTERM"];

for (const signal of signals) {
    process.on(signal, async () => {
        console.log(`Received ${signal}. Initiating graceful shutdown...`);
        await app.stop();
        await bot.stop();
        await posthog.shutdown();
        process.exit(0);
    });
}

For first, we should stop receiving updates - gracefully stop our backend API framework (for example, Elysia).

For second, we should process all pending updates - gracefully stop our bot with bot.stop method.

and last, we should call posthog.shutdown() which send captured analytics to our PostHog instance.

then we exit our process with 0 status code and it all!

this example shows how to gracefully shutdown your bot in right order for most applications.